Data storage systems often include cache memory for storing most frequently used data, also known as data “hot spots.” Typically the cache memory is stored on high speed storage media, such as a flash drive or a solid state disk, for improved accessibility. In many systems, the storage and removal of data from cache memory is based upon a priority queue where data priority is determined according to data transfer activity. For example, data may be deemed “hot” if it receives specified number of I/O hits over a certain time interval. When cache memory is substantially filled or at a critical size, the addition of new cache data results in removal of previously cached data residing at a lower priority tier. In some instances, invalid data that is associated with non-existent or corrupt files (e.g. deleted files) may persist in cache memory until the invalid data is replaced by higher priority data.